<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* #app{
            color: red;
        }
        .box{
            color: burlywood;
        }
        p{
            color: violet;
        } */
         /* #a{
            color: red;
         }
         .b{
            color: blue;
         }
         p{
            color: gold;
         }
         .app .box p{
            color: chartreuse;
         } */
         .box > div {
            color: maroon;
            background-color: pink;
            height: 30px;
         }
    </style>
</head>
<body>
    <div id="app" class="app">
        <div class="box">
            <!-- <div id="a" class="b">
                hello
                <div>css</div>
            </div>
            <div>word</div> -->
        </div>
    </div>
</body>
</html>